328 Mr. Parkinson on the Strata^ 



surfaces and rounclLh forms, evidently from attrition, and exhibit no 

 traces of organization, except when, as is very rarely the case, the 

 substance of the pebble is jasperised wood. The white quartz 

 pebbles, like quartz crystals, on being rubbed together, emit a strong 

 white lambent light, with a red fiery streak on the line of collision, 

 and an odour which much resembles that of the electric aura. 



2d. Oval or roundish, and rather flat siliceous pebbles, generally 

 surrounded by a crust or coat differing in colour and degree of trans- 

 parency from the internal substance, which also varies in different 

 specimens, in these respects, as v/ell as in the disposition of the parts 

 of which the substance is composed. In some this is spotted, or 

 clouded, in very beautiful forms ; in others it is marked by concen- 

 tric strias, as if the result of the successive application of distinct 

 laminGE : the prevailing colours in most of these pebbles being differ- 

 ent shades of yellow. In several the traces of marine remains are 

 observable : these are, in some the casts of anom'ia^ and the impres- 

 sions of the spines and plates of echini ; and in others, wdiich gene- 

 rally possess a degree of transparency, the remains of alcyotiia. 

 The impressions, though frequently on the- surface of the pebble, 

 seldom, if ever, appear to be in the least rubbed down ; thus seeming 

 to prove decidedly, that these pebbles have not been rounded 

 by rolling ; but that they owe their figures to the circumstances 

 under which they were originally formed : it is apprehended therefore, 

 that these pebbles have each been produced by a distinct chemical 

 formation, which, it may be safely concluded from the remains of 

 marine animals so frequently found in them, took place at the bottom 

 of the sea, while thase animals were yet living. 



The formation of these fossils at the bottom of a former sea, and 

 perhaps, on the identical spots in which they are now frequently 

 fouad, is more plainly evinced by pebbles agreeing in some peculiar 



